The present invention relates to a cathode ray tube provided with a bar code, and more particularly to a cathode ray tube having an improved bar code.
A bar code provides product identification information in order to computerize the management of processes during manufacturing, after delivery, etc., and is also provided and used in a cathode ray tube.
In a conventional cathode ray tube, as shown in FIG. 1, a sheet 40 on which a bar code is marked is most generally attached to a skirt 50 of cathode ray tube 10. The sheet 40 is generally formed of a heat resisting paint, on which is provided a bar code of a sharply contrasting color.
This conventional bar code providing method is overly difficult to implement because a liquid paint is coated and then dried on the skirt, into which the bar code itself is carved by a different paint in liquid form and dried. Moreover, the addition of this second paint material used for providing the bar code is burdensome and time-consuming.
U.S. Pat. No. 4,327,283 describes a glass workpiece with a bar code which consists of a thin, dark-colored undercoating and a thin, light-colored overcoating. The bar code marking may be made by depositing the coatings, each of which consists essentially of pigment particles and an alkali silicate binder, and then recessing the marking into and through the overcoating. The recessing may be achieved by ablating the overcoating with a laser beam. In U.S. Pat. No. 4,515,867, the undercoating contains an operative proportion of mica particles, and the overcoating is essentially free from mica, so as to increase resistance of the undercoating laser ablation.
Such improved coatings can be produced rapidly on an automatic machine which will also ablate the marking into the workpiece. However, the troublesome problems inherent to double-coating still remain.
It is, therefore, desirable to provide a bar code marking of a single coating layer having the properties required for a bar code of cathode ray tubes, for example, resistance to heat and chemicals, readability and adhesiveness to glass material.